Supplementation of yeast culture to low-fishmeal diets improves growth, intestinal health, and heat stress resistance in juvenile Chinese mitten crab (Eriocheir sinensis)

Yeast culture (YC), a microecological product derived from yeast fermentation, can enhance animal growth, health, and resistance to heat stress. However, its impact on the economically significant crustacean Eriocheir sinensis has not been demonstrated. This study investigated the effects of low-fishmeal YC on the growth, intestinal health, and heat stress resistance of juvenile Chinese mitten crabs. Crabs (0.72 ± 0.01 g) were distributed across 42 tanks, and 40 crabs were randomly maintained per tank in six replicates. The crabs were fed a control diet (35% fish meal) or six YC concentrations (15% fish meal; 0, 0.8, 1.6, 2.4, 3.2, or 4.0 g/kg) for 56 days. After sample collection, the remaining crabs were subjected to a 72-h heat stress challenge at 32 °C. A moderate-yield YC diet significantly improved weight gain, specific growth rate, and digestive enzyme activities (α-amylase, trypsin, and lipase) compared to those of crabs fed a 15% fishmeal diet without YC. Notably, the diet with 3.2 g/kg YC supplementation was performed as well as crabs fed a 35% fishmeal diet. YC also enhanced intestinal morphology in the low-fishmeal diet group and reduced oxidative damage by increasing the expression of genes related to the peritrophic membrane and tight junction proteins. Furthermore, YC supplementation diversified the intestinal microbiota, significantly increased the abundance of Firmicutes and the genus Shewanella, increased acetate and butyrate levels and decreased the abundance of Proteobacteria. Correlation analysis revealed that weight gain and specific growth rate were associated with most digestive activity and intestinal health indicators. Following heat stress challenge, YC protected against oxidative stress and enhanced serum immunity at elevated temperatures. This study indicated that incorporating YC in low-fishmeal diets significantly increases juvenile crab growth, improves intestinal health, and mitigates oxidative stress induced by temperature elevation. The optimal YC concentration was determined to be 2.71 g/kg through regression analysis.